US20240077783A1 - Image capturing apparatus capable of reducing exposure variation between upper and lower end areas of image, method of controlling image capturing apparatus, and storage medium - Google Patents

Image capturing apparatus capable of reducing exposure variation between upper and lower end areas of image, method of controlling image capturing apparatus, and storage medium Download PDF

Info

Publication number
US20240077783A1
US20240077783A1 US18/452,171 US202318452171A US2024077783A1 US 20240077783 A1 US20240077783 A1 US 20240077783A1 US 202318452171 A US202318452171 A US 202318452171A US 2024077783 A1 US2024077783 A1 US 2024077783A1
Authority
US
United States
Prior art keywords
light emission
shutter
speed
photographing
image capturing
Prior art date
Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
Pending
Application number
US18/452,171
Other languages
English (en)
Inventor
Yukihiro Matsumoto
Current Assignee (The listed assignees may be inaccurate. Google has not performed a legal analysis and makes no representation or warranty as to the accuracy of the list.)
Canon Inc
Original Assignee
Canon Inc
Priority date (The priority date is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the date listed.)
Filing date
Publication date
Application filed by Canon Inc filed Critical Canon Inc
Assigned to CANON KABUSHIKI KAISHA reassignment CANON KABUSHIKI KAISHA ASSIGNMENT OF ASSIGNORS INTEREST (SEE DOCUMENT FOR DETAILS). Assignors: MATSUMOTO, YUKIHIRO
Publication of US20240077783A1 publication Critical patent/US20240077783A1/en
Pending legal-status Critical Current

Links

Images

Classifications

    • G—PHYSICS
    • G03—PHOTOGRAPHY; CINEMATOGRAPHY; ANALOGOUS TECHNIQUES USING WAVES OTHER THAN OPTICAL WAVES; ELECTROGRAPHY; HOLOGRAPHY
    • G03B—APPARATUS OR ARRANGEMENTS FOR TAKING PHOTOGRAPHS OR FOR PROJECTING OR VIEWING THEM; APPARATUS OR ARRANGEMENTS EMPLOYING ANALOGOUS TECHNIQUES USING WAVES OTHER THAN OPTICAL WAVES; ACCESSORIES THEREFOR
    • G03B7/00—Control of exposure by setting shutters, diaphragms or filters, separately or conjointly
    • G03B7/16—Control of exposure by setting shutters, diaphragms or filters, separately or conjointly in accordance with both the intensity of the flash source and the distance of the flash source from the object, e.g. in accordance with the "guide number" of the flash bulb and the focusing of the camera
    • G—PHYSICS
    • G03—PHOTOGRAPHY; CINEMATOGRAPHY; ANALOGOUS TECHNIQUES USING WAVES OTHER THAN OPTICAL WAVES; ELECTROGRAPHY; HOLOGRAPHY
    • G03B—APPARATUS OR ARRANGEMENTS FOR TAKING PHOTOGRAPHS OR FOR PROJECTING OR VIEWING THEM; APPARATUS OR ARRANGEMENTS EMPLOYING ANALOGOUS TECHNIQUES USING WAVES OTHER THAN OPTICAL WAVES; ACCESSORIES THEREFOR
    • G03B15/00—Special procedures for taking photographs; Apparatus therefor
    • G03B15/02—Illuminating scene
    • G03B15/03—Combinations of cameras with lighting apparatus; Flash units
    • G03B15/05—Combinations of cameras with electronic flash apparatus; Electronic flash units
    • G—PHYSICS
    • G03—PHOTOGRAPHY; CINEMATOGRAPHY; ANALOGOUS TECHNIQUES USING WAVES OTHER THAN OPTICAL WAVES; ELECTROGRAPHY; HOLOGRAPHY
    • G03B—APPARATUS OR ARRANGEMENTS FOR TAKING PHOTOGRAPHS OR FOR PROJECTING OR VIEWING THEM; APPARATUS OR ARRANGEMENTS EMPLOYING ANALOGOUS TECHNIQUES USING WAVES OTHER THAN OPTICAL WAVES; ACCESSORIES THEREFOR
    • G03B9/00—Exposure-making shutters; Diaphragms
    • G03B9/70—Exposure-making shutters; Diaphragms with flash-synchronising contacts
    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04N—PICTORIAL COMMUNICATION, e.g. TELEVISION
    • H04N23/00—Cameras or camera modules comprising electronic image sensors; Control thereof
    • H04N23/70—Circuitry for compensating brightness variation in the scene
    • H04N23/73—Circuitry for compensating brightness variation in the scene by influencing the exposure time
    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04N—PICTORIAL COMMUNICATION, e.g. TELEVISION
    • H04N23/00—Cameras or camera modules comprising electronic image sensors; Control thereof
    • H04N23/70—Circuitry for compensating brightness variation in the scene
    • H04N23/74—Circuitry for compensating brightness variation in the scene by influencing the scene brightness using illuminating means
    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04N—PICTORIAL COMMUNICATION, e.g. TELEVISION
    • H04N23/00—Cameras or camera modules comprising electronic image sensors; Control thereof
    • H04N23/70—Circuitry for compensating brightness variation in the scene
    • H04N23/745—Detection of flicker frequency or suppression of flicker wherein the flicker is caused by illumination, e.g. due to fluorescent tube illumination or pulsed LED illumination

Definitions

  • the present invention relates to an image capturing apparatus that is capable of reducing exposure variation between upper and lower end areas of an image, a method of controlling the image capturing apparatus, and a storage medium.
  • a focal plane-type shutter of an image capturing apparatus has a front curtain for starting exposure and a rear curtain for terminating exposure.
  • the types of the shutter include one that has the front and rear curtains each using a mechanical shutter system (mechanical shutter type) and one that has the front and rear curtains each using an electronic shutter system (electronic shutter type). Further, the types of the shutter also include a mixed type having the front curtain using the electronic shutter system and the rear curtain using the mechanical shutter system (electronic front curtain type).
  • flash light emission is permitted when the shutter fully opens for an image sensor, that is, when traveling of the front curtain of the shutter is completed. Then, after the flash light emission, the rear curtain is caused to travel at a timing when the peak value of a signal becomes a predetermined amount of light compared with the maximum value of the amount of light emission.
  • a shutter speed is determined at which a shutter-fully open time period during which the shutter is fully open becomes the shortest.
  • the shutter-fully open time period corresponding to the shutter speed is referred to as the flash synchronization time.
  • Japanese Laid-Open Patent Publication (Kokai) No. 2008-060640 discloses a technique for shortening, when flash photographing is performed in an image capturing apparatus of the electronic front curtain type, the flash synchronization time by always making the traveling time of the electronic shutter of the front curtain shorter than the traveling time of the mechanical shutter of the rear curtain to advance the light emission timing.
  • the present invention provides an image capturing apparatus that is capable of reducing exposure variation between upper and lower end areas of an image when photographing is performed with flash light emission while shortening a flash synchronization time, a method for controlling the image capturing apparatus, and a storage medium.
  • an image capturing apparatus including at least one processor, and a memory coupled to the at least one processor, the memory having instructions that, when executed by the processor, perform the operations as a determination unit configured to determine parameters including a shutter speed before flash light emission photographing is performed, and a control unit configured to selectively execute first control for controlling a traveling speed of a front curtain of a shutter and a traveling speed of a rear curtain of the shutter to the same speed, and second control for controlling the traveling speed of the front curtain to be higher than the traveling speed of the rear curtain, wherein, before flash light emission photographing is performed, the control unit determines which of the first control and the second control is to be adopted according to the shutter speed in the parameters, which is determined by the determination unit.
  • a method of controlling an image capturing apparatus including determining parameters including a shutter speed before flash light emission photographing is performed, and performing selective execution of first control for controlling a traveling speed of a front curtain of a shutter and a traveling speed of a rear curtain of the shutter to the same speed, and second control for controlling the traveling speed of the front curtain to be higher than the traveling speed of the rear curtain, wherein said selective execution includes, before flash light emission photographing is performed, determining which of the first control and the second control is to be adopted according to the shutter speed in the determined parameters.
  • the present invention it is possible to reduce exposure variation between upper and lower end areas of an image when photographing is performed with flash light emission while shortening the flash synchronization time.
  • FIG. 1 is a block diagram of an image capturing apparatus.
  • FIG. 2 is a conceptual diagram showing a relationship between a travel pattern of a front curtain and a travel pattern of a rear curtain.
  • FIG. 3 is another conceptual diagram showing a relationship between a travel pattern of the front curtain and a travel pattern of the rear curtain.
  • FIG. 4 is another conceptual diagram showing a relationship between a travel pattern of the front curtain and a travel pattern of the rear curtain.
  • FIG. 5 is another conceptual diagram showing a relationship between a travel pattern of the front curtain and a travel pattern of the rear curtain.
  • FIG. 6 is a flowchart of a still image photographing process.
  • FIG. 7 is a flowchart of a flash synchronization shutter speed-increasing operation process.
  • FIGS. 8 A to 8 D are diagrams useful in explaining a range captured by an image sensor.
  • FIG. 9 is a conceptual diagram showing a relationship between a travel pattern of the front curtain and a travel pattern of the rear curtain in a case where an image capturing range is changed.
  • FIG. 10 is a flowchart of a variation of the flash synchronization shutter speed-increasing operation process.
  • FIG. 1 is a block diagram of an image capturing apparatus according to an embodiment of the present invention.
  • This image capturing apparatus is a digital camera (hereafter simply referred to as the camera) by way of example.
  • One or more of functional blocks appearing in FIG. 1 may be realized by hardware, such as an application-specific integrated circuit (ASIC) or a programmable logic array (PLA), or may be realized by a programmable processor, such as a central processing unit (CPU) or a micro processing unit (MPU), executing software.
  • ASIC application-specific integrated circuit
  • PDA programmable logic array
  • CPU central processing unit
  • MPU micro processing unit
  • one or more of the functional blocks may be realized by a combination of software and hardware. Therefore, even in a case where different functional blocks are described as operation subjects in the following description, the functional blocks may be realized by the same hardware as an operation subject.
  • the camera 1 includes a camera unit 100 , an external recording medium 200 , a lens unit 300 , and a flash unit 400 , and is a so-called lens-interchangeable type image capturing apparatus but is not limited to this.
  • the camera 1 may be configured such that the camera unit 100 and at least one of the lens unit 300 and the flash unit 400 are integrally formed with each other.
  • the type of front and rear curtains of a shutter 102 may be either a mechanical shutter type or an electronic shutter type insofar as the control of elements including a traveling speed can be changed. If both of the front and rear curtains are of the mechanical shutter type, the shutter 102 functions as a light blocking member for opening and blocking an optical path between the lens unit 300 and an image sensor 103 . If the front curtain is of the electronic shutter type, charges accumulated in the image sensor 103 in a horizontal direction are reset by front curtain control. If the rear curtain is of the electronic shutter type, charges accumulated in each line of the image sensor 103 are sequentially read out by rear curtain control.
  • the front curtain is of the electronic shutter type
  • the rear curtain is of the mechanical shutter type or the electronic shutter type, but this is not limitative.
  • the image sensor 103 is a charge-accumulating type solid-state image sensor, such as a charge coupled device (CCD) or a complementary metal-oxide semiconductor (CMOS) sensor, and generates analog image data by photoelectrical conversion of light flux incident through the lens unit 300 from an object (image capturing of the object).
  • An electronic viewfinder 105 uses a thin-film transistor (TFT)-type liquid crystal display (LCD), an organic electroluminescence (EL) device, or the like, and enables a user to confirm an object image.
  • TFT thin-film transistor
  • LCD liquid crystal display
  • EL organic electroluminescence
  • An analog-to-digital conversion section 106 converts analog image data output from the image sensor 103 to digital image data.
  • An image processor 107 performs a variety of processing operations, including white balance adjustment processing and gradation processing, on the digital image data output from the analog-to-digital conversion section 106 .
  • a timing generation section 108 generates signals (clock signal and the like control signals) for operating the image sensor 103 , the analog-to-digital conversion section 106 , a digital-to-analog conversion section 109 , and so forth. Further, the timing generation section 108 can control accumulation and readout of charges in the image sensor 103 by controlling the reset timing and the readout timing of the accumulated charges in the image sensor 103 .
  • the timing generation section 108 is controlled by a system controller 120 .
  • a memory controller 110 controls the analog-to-digital conversion section 106 , the image processor 107 , the digital-to-analog conversion section 109 , and a compression and decompression unit 111 to perform processing for writing acquired image data into a display memory 112 or a recording memory 113 .
  • a TFT-type LCD, an organic EL element, or the like is adopted for an image display section 114 .
  • Digital image data for display, written in the display memory 112 is converted to analog image data for display by the digital-to-analog conversion section 109 , and then displayed on the electronic viewfinder 105 or the image display section 114 .
  • the recording memory 113 has a storage capacity sufficient to store a predetermined number of still image data items and moving image data items, and stores image data acquired by capturing images of objects.
  • the recording memory 113 can also be used as a work area for the system controller 120 .
  • the compression and decompression unit 111 reads image data stored in the recording memory 113 and compresses and decompresses the read image data by a predetermined image compression method and an image decompression method, respectively, according to a variety of uses.
  • a shutter controller 115 controls the operation of the shutter 102 based on a result of photometry on an object, which is calculated by the system controller 120 .
  • the shutter 102 can be controlled in conjunction with a diaphragm 302 .
  • the system controller 120 performs centralized control of the operations of the camera 1 . Based on image data captured by the image sensor 103 , the system controller 120 performs exposure control, and focus control according to a result of focus detection. For example, the system controller 120 uses the image data captured by the image sensor 103 to perform lens position control (focus control) based on contrast information of the image data acquired while shifting the position of the focus lens. Further, as another focus control method, the system controller 120 may adopt a method of detecting an in-focus state of an optical image from a phase difference between two images of an object based on the captured image data and performing the lens position control (focus control) based on a result of this focus detection.
  • the system controller 120 can also perform flicker detection for detecting whether or not there is a flicker in a photographing environment, using the captured image data. Further, the system controller 120 can also perform the photometry operation for calculating a luminance value of an object using the captured image data. As the exposure control performed when capturing an image of an object to acquire image data, the system controller 120 adjusts exposure parameters, including an aperture value, a shutter speed, and a photographic sensitivity (ISO speed).
  • exposure parameters including an aperture value, a shutter speed, and a photographic sensitivity (ISO speed).
  • the aperture value is a parameter related to the opening of the diaphragm 302 .
  • the shutter speed is a parameter related to the charge accumulation time in the image sensor 103 .
  • the photographic sensitivity is a parameter related to an analog gain amount and a digital gain amount.
  • the system controller 120 controls the flash unit 400 according to a result of the photometry operation, camera settings, and a state of the flash unit 400 to thereby control the amount of light emission and the light emission timing of the flash unit 400 . Further, the system controller 120 can switch the image capturing range of the image sensor 103 according to user settings set by operating an operation section 133 , to thereby perform photographing using pixel outputs from the whole surface of the image sensor or photographing using pixel outputs from a cut-out part of the whole surface.
  • the system controller 120 can perform proper exposure and flash control dependent on the luminance value of the object, and change a range of image capturing by the image sensor 103 .
  • a nonvolatile memory 123 is an electrically erasable programmable read-only memory (EEPROM), represented e.g. by a flash memory, and data can be electrically stored and erased.
  • EEPROM electrically erasable programmable read-only memory
  • Each operating member is formed by a button, a switch, a dial, a touch panel, a sight line detection device, or a voice recognition device, or by a combination of ones of these components.
  • a mode dial 130 is used when a user sets a desired photographing mode by selecting from a plurality of photographing modes that can be set by the camera unit 100 .
  • the photographing modes that can be set include a still image mode for photographing a still image and a moving image mode for recording a moving image.
  • the exposure parameters can be automatically or manually set, including an automatic mode, a program mode, an aperture priority mode, a shutter speed priority mode, and a manual mode.
  • the user can set whether or not to perform flash light emission when photographing a still image.
  • the live view display function for displaying an image (live view image) on the electronic viewfinder 105 or the image display section 114 for the user to confirm an object.
  • the live view display function is for sequentially displaying a plurality of acquired image data items by continuously executing charge accumulation (image capturing) using the image sensor 103 .
  • a shutter switch 131 is used for instructing the start of a photographing preparation operation or a photographing operation for an object.
  • a SW1 of the shutter switch 131 is turned on by a first stroke (e.g. half-pressing) of the shutter switch 131 .
  • the system controller 120 starts the focus control, the exposure control, and the auto white balance (AWB) processing, and so forth.
  • a SW2 of the shutter switch 131 is turned on by a second stroke (e.g. full-pressing) of the shutter switch 131 .
  • the SW2 is turned on, the photographing operation is started, and the system controller 120 starts exposure processing and recording processing related to charge accumulation (image capturing) using the image sensor 103 .
  • signals read from the image sensor 103 are written into the recording memory 113 as image data via the analog-to-digital conversion section 106 and the memory controller 110 .
  • development processing based on a variety of arithmetic operations performed by the image processor 107 and the memory controller 110 is performed on this image data, and the developed image data is written into the recording memory 113 .
  • the image data subjected to the development processing which is read from the recording memory 113 , is compressed by the compression and decompression unit 111 according to an instruction from the system controller 120 . Then, in response to an instruction from the system controller 120 , the compressed image data is written into a recording section 201 of the external recording medium 200 via a first camera interface (I/F) 140 , a first camera connector 141 , a media connector 203 , and a media I/F 202 .
  • I/F first camera interface
  • a reproduction switch 132 is used to instruct the start of reproduction processing.
  • acquired image data is read from the recording memory 113 or the external recording medium 200 and is displayed on the image display section 114 .
  • the operation section 133 is used to configure a variety of settings associated with menu display and photographing, and a variety of settings associated with reproduction.
  • the user can set not only a variety of settings for flash photographing, and a shutter speed, an aperture value, an ISO speed, and so forth, which are used at the time of photographing, but also an image capturing range of the image sensor 103 , as will be described hereinafter with reference to FIG. 8 .
  • the user can also set whether or not to perform flash light emission when photograph a still image, a shutter speed at the time of flash photographing, and so forth.
  • a power switch 134 is used to switch on/off power supply to the components of the camera 1 from a power source (battery), not shown. Note that by operating the power switch 134 , it is possible to switch power supply not only to the camera unit 100 but also to a variety of accessory devices connected to the camera unit 100 , including the lens unit 300 and the external recording medium 200 .
  • a power supply controller 124 includes a battery detection circuit, a DC-DC converter, a switch circuit used to switch between blocks to be energized, and so forth.
  • the power supply controller 124 detects whether or not a battery is attached, and a type and a remaining amount of the battery, and supplies required voltage to the components of the camera 1 for a required time period, based on an instruction given from the system controller 120 according to an operation of the power switch 134 .
  • a second camera I/F 150 is provided in a camera mount 160 for connecting between the camera unit 100 and the lens unit 300 .
  • a second camera connector 151 connected to the second camera I/F 150 electrically connects between the camera unit 100 and the lens unit 300 via a lens connector 311 and a lens I/F 310 .
  • a third camera I/F 170 is an interface for connecting between the camera unit 100 and the flash unit 400 .
  • a third camera connector 171 connected to the third camera I/F 170 electrically connects between the camera unit 100 and the flash unit 400 via a flash unit connector 411 and a flash unit I/F 410 .
  • the second camera connector 151 and the third camera connector 171 transmit control signals, status signals, data signals, and the like, between the camera unit 100 , and the lens unit 300 and the flash unit 400 . Further, it is possible to supply current of various voltages to the lens unit 300 and the flash unit 400 via the second camera connector 151 and the third camera connector 171 .
  • the second camera connector 151 and the third camera connector 171 may be configured to be capable of transmitting not only electrical communication but also optical communication, voice communication, and so forth.
  • the external recording medium 200 is an external recording device, such as a memory card and a hard disk.
  • the external recording medium 200 is equipped with the recording section 201 implemented e.g. by a semiconductor memory or a magnetic disk, and the media I/F 202 for interfacing with the camera unit 100 . Further, the external recording medium 200 is also equipped with the media connector 203 for connection to the camera unit 100 .
  • the lens unit 300 is an optical device which can be attached to and removed from the camera unit 100 .
  • a lens mount 320 is engaged with the camera mount 160 to make the lens unit 300 mechanically attachable to the camera unit 100 .
  • the lens connector 311 is provided inside the lens mount 320 , for electrically connecting between the lens unit 300 and the camera unit 100 .
  • the lens connector 311 transmits control signals, status signals, data signals, and so forth, between the lens unit 300 and the camera unit 100 .
  • a photographic lens group 301 is an optical member including a focus lens, a zoom lens, a shift lens, and so forth.
  • the diaphragm 302 adjusts the light amount of light flux from an object, which passes through the photographic lens group 301 and enters the image sensor 103 .
  • An aperture controller 303 controls the opening amount of the diaphragm 302 according to an instruction from the system controller 120 .
  • the system controller 120 instructs the aperture controller 303 to change the aperture diameter of the diaphragm 302 such that the opening amount of the diaphragm 302 becomes equal to an opening amount corresponding to a target aperture value.
  • the aperture diameter of the diaphragm 302 is sequentially detected by intercommunication between the lens unit 300 and the camera unit 100 . Then, when the aperture diameter of the diaphragm 302 reaches the aperture diameter corresponding to the target aperture value, the system controller 120 terminates changing the aperture diameter of the diaphragm 302 .
  • a lens controller 304 controls the operation (driving) of the photographic lens group 301 .
  • the lens controller 304 can detect a lens position (focal position) of the focus lens, and information on the detected lens position is transmitted to the camera unit 100 .
  • a lens system controller 305 performs centralized control of the lens unit 300 .
  • the lens system controller 305 incorporates a CPU, a volatile memory, and a nonvolatile memory, none of which are shown.
  • the volatile memory stores constants, variables, programs for the operations, and so forth, and the nonvolatile memory stores identification information, such as a unique number associated with the lens unit 300 , management information, and functional information, such as an open aperture value, a minimum aperture value, and a focal length.
  • the flash unit 400 is an accessory (flash device) which can be attached to and removed from the camera unit 100 .
  • the flash unit connector 411 transmits control signals, status signals, data signals, and so forth, between the flash unit 400 and the camera unit 100 . Further, it is also possible to receive and supply current of various voltages via the flash unit connector 411 .
  • the flash unit connector 411 may be configured to be capable of transmitting not only electrical communication but also optical communication, voice communication, and the like.
  • a flash unit controller 402 performs light emission control according to an amount of light emitted by a flash light emitting section 401 and a variety of settings of the flash unit 400 .
  • FIGS. 2 to 5 are conceptual diagrams each showing a relationship between a travel pattern of the front curtain and a travel pattern of the rear curtain in the electronic front-curtain system.
  • a curve indicated by a symbol S1 represents a scanning pattern (traveling curve) of reset scan performed by the electronic front curtain.
  • a curve indicated by a symbol S2 represents a raveling curve of the mechanical rear curtain.
  • both of the front curtain and the rear curtain are of the mechanical shutter type, the image sensor 103 is exposed to light by traveling of the front curtain of the shutter, and blocked from light by the rear curtain of the shutter. If both of the front curtain and the rear curtain are of the electronic shutter type, accumulated charges in the image sensor 103 in a horizontal direction are reset by the front curtain control, and charges accumulated in each line of the image sensor 103 are sequentially read out by the rear curtain control.
  • time T1 represents a traveling time of the front curtain of the shutter.
  • the time T1 is a time period required for the front curtain to perform charge accumulation reset scan of the image sensor 103 .
  • a light emission amount curve represents temporal changes in the light emission amount occurring when flash light emission is performed.
  • a maximum value of the light emission amount is represented by 1, and an amount of light emission reduced to half of the maximum value is represented by 1 ⁇ 2.
  • a time period from the start of flash light emission to a time at which the amount of light emission is reduced to half to start traveling of the rear curtain is represented by time T2.
  • the traveling of the rear curtain is started after the light amount is reduced to a predetermined amount, and hence the time T2 is a full open section during which the shutter is fully open, and a time period obtained by T1+T2 is the flash synchronization time.
  • a traveling speed of the front curtain is a speed of reset scan performed on accumulated charges in the image sensor 103 and corresponds to an inclination of the curve S1.
  • a traveling speed of the rear curtain is a speed at which a leading edge of the mechanical rear curtain passes over the imaging surface of the image sensor 103 and corresponds to an inclination of the curve S2.
  • the flash synchronization time is determined by the time T1 as the traveling time of the front curtain and the time T2 as the full open section.
  • the traveling speed of the shutter reducing a reset time period or a readout time period for accumulated charges, in the case of the electronic shutter
  • reducing a light emission time period reducing the light emission amount or making earlier the time at which the light emission amount is reduced to half.
  • FIG. 3 is a diagram showing an example of control for shortening the flash synchronization time by increasing the traveling speed of the front curtain.
  • the traveling speed of the front curtain By increasing the traveling speed of the front curtain, the inclination of the curve S1 becomes large, and the time T1 is reduced. This makes it possible to advance the start timing of flash light emission, whereby the flash synchronization time is shortened.
  • FIG. 4 is a diagram showing an example of control for shortening the flash synchronization time by limiting the amount of flash light emission. Note that the heights of the peaks of the light emission amounts in FIGS. 2 to 5 are expressed in relative amounts, and the light emission amounts in FIGS. 4 and 5 are smaller than the light emission amounts in FIGS. 2 and 3 . As shown in FIG. 4 , by limiting the amount of flash light emission, the time T2 is shortened. This makes it possible to advance the traveling start time of the rear curtain, whereby the flash synchronization time is shortened.
  • FIG. 5 is a diagram showing an example of control for shortening the flash synchronization time by increasing the traveling speed of the front curtain and limiting the amount of flash light emission at the same time.
  • both of the effect described with reference to FIG. 3 and the effect described with reference to FIG. 4 are reflected, and hence the flash synchronization time is shortened.
  • FIG. 6 is a flowchart of a still image photographing process. This process is realized, for example, by a CPU of the system controller 120 , loading a program stored in a ROM of the same, into a RAM of the same, and executing the loaded program. This process is started when the camera 1 is powered on. This process is terminated when the camera 1 is powered off.
  • a step S 101 the system controller 120 shifts the camera 1 to a photographing standby state and performs the live view display.
  • the system controller 120 determines whether or not the SW1 of the shutter switch 131 is turned on. If the SW1 is not turned on, the system controller 120 returns to the step S 101 , whereas if the SW1 is turned on, the system controller 120 proceeds to a step S 103 .
  • the system controller 120 performs a ranging operation based on an image captured by the image sensor 103 and controls the photographic lens group 301 to adjust the focus based on a result of the ranging operation.
  • the system controller 120 performs a photometry operation based on the image captured by the image sensor 103 .
  • any suitable method including a well-known method may be adopted.
  • the system controller 120 calculates an averaged luminance of each of a plurality of blocks (regions) into which the whole captured image is divided. Then, an averaged luminance of all the blocks is calculated, as a photometry result, from the averaged luminances of the blocks by applying a predetermined weight thereto, and the system controller 120 further performs, based on the photometry result, operations including determination of whether or not to cause the flash unit 400 to emit light at the time of still image photographing, and calculation of control values used when photographing is performed.
  • a step S 105 the system controller 120 waits until the SW2 of the shutter switch 131 is turned on, and when the SW2 is turned on, the system controller 120 proceeds to a step S 106 .
  • the system controller 120 determines whether or not to perform flash light emission photographing according to the photometry result obtained in the step S 104 and the settings of the camera unit 100 .
  • the flash light emission photographing refers to causing the flash unit 400 to emit light when a still image is photographed. If forced light emission has been set, it is determined that flash light emission photographing is to be performed. If automatic light emission has been set, whether or not to perform flash light emission photographing is determined based on the photometry result.
  • the system controller 120 proceeds to a step S 111 , whereas if it is determined that flash light emission photographing is to be performed, the system controller 120 proceeds to a step S 107 .
  • the system controller 120 calculates the photographing parameters (a time value (Tv), an aperture value (Av), and an ISO speed) for flash light emission photographing, based on the photometry result obtained in the step S 104 and a condition that photographing is to be performed with flash light emission. That is, the system controller 120 calculates the photographing parameters, such as a shutter speed (or a Tv value), an aperture value, and an ISO speed, for the case where still image photographing is performed with flash light emission.
  • Tv is an expression corresponding to an acronym of “time value”, but in actuality in the present embodiment, the Tv value is used to mean a corresponding shutter speed.
  • a step S 108 the system controller 120 performs light control calculation to determine an amount of flash light emission at the time of still image photographing.
  • the amount of flash light emission, calculated here, is referred to as the “provisionally determined flash light emission amount”.
  • a step S 109 the system controller 120 executes a flash synchronization shutter speed-increasing operation process (see FIG. 7 ), described hereinafter.
  • the system controller 120 causes flash light to be emitted in a step S 110 and performs the still image photographing in a step S 112 .
  • the amount of light emission in the step S 110 is sometimes set to a different amount (limited value) from the provisionally determined flash light emission amount by the flash synchronization shutter speed-increasing operation process (see FIG. 7 ).
  • the system controller 120 calculates the photographing parameters for flash light non-emission based on the photometry result obtained in the step S 104 . That is, the system controller 120 calculates the photographing parameters, such as a shutter speed (or a Tv value), an aperture value, and an ISO speed, for the case where still image photographing is performed without flash light emission. Then, the system controller 120 proceeds to the step S 112 .
  • the photographing parameters such as a shutter speed (or a Tv value), an aperture value, and an ISO speed
  • a step S 113 the system controller 120 waits until the shutter switch 131 is released (SW1 is turned off) after the still image photographing, and if the shutter switch 131 is released, the system controller 120 terminates the still image photographing process in FIG. 6 . Note that after it is determined that the answer to the question of the step S 113 is affirmative (YES), the process may return to the step S 101 .
  • FIG. 7 is a flowchart of the flash synchronization shutter speed-increasing operation process performed in the step S 109 in FIG. 6 .
  • a step S 201 the system controller 120 acquires the photographing parameters (Tv value, Av value, and ISO speed) for flash light emission photographing, calculated in the step S 107 .
  • the system controller 120 checks whether the shutter speed is a high speed, an intermediate speed, or a low speed. Then, the process is branched to one of steps S 206 , S 205 and S 203 according to a result of the check.
  • TV0 and TV1 are used as threshold values to be compared with the Tv value as a photographing parameter.
  • the threshold value TV0 corresponds to a first shutter speed
  • the threshold value TV1 corresponds to a second shutter speed.
  • the magnitude relation between the threshold values is TV1>TV0.
  • the system controller 120 proceeds to a step S 206 .
  • the system controller 120 proceeds to a step S 205 .
  • the system controller 120 proceeds to a step S 203 .
  • the system controller 120 determines whether or not to perform front curtain correction control (second control) for correcting the traveling speed of the front curtain.
  • the front curtain correction control is control for making the traveling speed of the front curtain of the shutter higher than the traveling speed of the rear curtain of the shutter.
  • a front curtain correction execution flag is set to 1.
  • the traveling speed of the front curtain of the shutter is controlled such that it is equal to the traveling speed of the rear curtain of the shutter (first control).
  • the front curtain correction execution flag is reset to 0.
  • the system controller 120 selectively executes the first control and the second control.
  • the system controller 120 determines whether or not the provisionally determined flash light emission amount is equal to or larger than a predetermined light emission amount (light emission amount check). Then, if the provisionally determined flash light emission amount is equal to or larger than the predetermined light emission amount, it can be determined that at the current shutter speed, the time period over which flash light emission is performed does not properly fall within the full open section during which the shutter is fully open, and hence the system controller 120 proceeds to a step S 204 .
  • the system controller 120 limits the flash light emission amount at the time of photographing to a value smaller than the provisionally determined flash light emission amount (light emission amount clip).
  • the system controller 120 proceeds to the step S 205 .
  • the step S 205 to which the process proceeds from the step S 203 or the step S 204 , since the determined shutter speed is the high speed, it is not appropriate to lower the actual shutter speed for the flash synchronization time. Accordingly, in the step S 205 , the system controller 120 sets the front-curtain correction execution flag (sets the flag to 1). With this, in the step S 110 et seq. in FIG. 6 , the traveling speed of the front curtain of the shutter is controlled to be higher than the traveling speed of the rear curtain of the shutter according to the determined shutter speed.
  • the process proceeds to the step S 205 without executing the step S 204 , although the front curtain correction control is performed, the light emission amount clip is not applied, and hence the traveling patterns of the front curtain and the rear curtain are as shown in the illustrated example in FIG. 3 .
  • the front curtain correction control is performed and also the light emission amount clip is applied, and hence the traveling patterns of the front curtain and the rear curtain are as shown in the illustrated example in FIG. 5 .
  • the determined shutter speed is the medium speed, and hence it is not appropriate to lower the actual shutter speed for the flash synchronization time.
  • the system controller 120 sets the front curtain correction execution flag (sets the flag to 1).
  • the traveling speed of the front curtain of the shutter is controlled to be higher than the traveling speed of the rear curtain of the shutter according to the determined shutter speed.
  • the front curtain correction control is performed but the light emission amount clip is not applied, and hence the traveling patterns of the front curtain and the rear curtain are as shown in the illustrated example in FIG. 3 .
  • the system controller 120 resets the front curtain correction execution flag (sets the flag to 0). Therefore, in the step S 110 et seq. in FIG. 6 , the front curtain and the rear curtain are controlled to travel at the same speed. This reduces exposure variation (exposure deviation) between the upper and lower end areas of the image. Since neither the front curtain correction control is performed nor the light emission clip is applied, the traveling patterns of the front and rear curtains are as shown in the illustrated example in FIG. 2 .
  • the system controller 120 After execution of the steps S 205 or 206 , the system controller 120 terminates the flash synchronization shutter speed-increasing operation process in FIG. 7 .
  • the front and rear curtains of the shutter are controlled to the same speed, and hence it is possible to perform photographing such that the exposure variation between the upper and lower end areas of the screen is reduced (the step S 206 ).
  • the shutter speed is high enough to satisfy the condition of Tv value ⁇ TV0 so that the front and rear curtains are controlled to respective different traveling speeds, if the provisionally determined flash light emission amount is equal to or larger than the predetermined light emission amount, the emission amount clip is applied, so that the exposure variation between the upper and lower end areas of the screen is less liable to be caused.
  • the system controller 120 as a determination unit determines the photographing parameters including the shutter speed before flash light emission photographing is performed (the step S 107 ).
  • the system controller 120 as a control unit determines whether to adopt execution of the front curtain correction control (second control) or non-execution of the front curtain correction control (first control) when photographing is performed, according to the shutter speed in the determined photographing parameters (the step S 202 ).
  • the system controller 120 adopts the first control (the step S 206 ) in a case where the determined shutter speed is lower than the first shutter speed (TV0>Tv value) and adopts the second control (the step S 205 ) in a case where the shutter speed is equal to or higher than the first shutter speed (TV ⁇ TV0).
  • the system controller 120 controls the amount of flash light emission at the time of photographing, based on the shutter speed and the provisionally determined flash light emission amount. More specifically, in a case where the shutter speed is equal to or higher than the second shutter speed (Tv value ⁇ TV1) and also the provisionally determined flash light emission amount is equal to or larger than the predetermined amount of light emission, the system controller 120 limits the amount of flash light emission at the time of photographing to a value smaller than the provisionally determined flash light emission amount (the step S 204 ). In this case, the second control (the step S 205 ) is further adopted. This makes it possible to more effectively shorten the flash synchronization time in a case where there is a high need of making the shutter speed high.
  • the changes in the positions of the front curtain and the rear curtain from the start to the end of traveling of the shutter may be linear or nonlinear.
  • the threshold values TV0 and TV1, and the predetermined amount of light emission are all set to respective fixed values. However, this is not limitative, but each value may be variable, or a plurality of candidate values may be held for each value and a candidate value to be actually applied may be selected.
  • first shutter speed and the second shutter speed are set to the different values, they may be set to the same value.
  • steps S 203 and S 204 may be eliminated from FIG. 7 and FIG. 10 , referred to hereinafter.
  • the first and second shutter speeds (or the threshold values TV0 and TV1), and the predetermined amount of light emission may be variably controlled based on photometric information. For example, when the photometric information is acquired, if the photographing luminance is dark, the flash light becomes dominant in photographing, and hence exposure variation caused by the speed difference between the front curtain and the rear curtain of the shutter is less noticeable. However, if the photographing luminance is bright, exposure to external light is also important. Therefore, at least one of the threshold values TV0 and TV1 or the predetermined amount of light emission may be switched, according to the photographing luminance. For example, in a case where the photographing luminance is dark, the threshold values TV0 and TV1 may be changed to smaller values (the first shutter speed and the like may be changed to a lower value).
  • the threshold values TV0 and TV1 may also be changed in a case where the image capturing range of the image sensor 103 changes. This will be described with reference to FIGS. 8 A to 8D and 9 .
  • FIGS. 8 A to 8D are diagrams useful in explaining an image capturing range of the image sensor 103 .
  • an original image capturing range in a case where the whole effective area of the image sensor 103 is used is as illustrated in FIG. 8 A .
  • a length in a vertical direction (vertical length) in the original image capturing range is denoted by h1.
  • An image capturing range obtained by applying an aspect ratio of 16:9 to the original image capturing range is indicated by solid lines in FIG. 8 B , and its vertical length is denoted by h2.
  • the image capturing range of an Advanced Photo System type-C (APS-C) size is indicated by solid lines in FIG. 8 C in comparison with the original image capturing range, and its vertical length is denoted by h3.
  • the image capturing range obtained by applying the aspect ratio of 16:9 to the image capturing range of the APS-C size is indicated by solid lines in FIG. 8 D , and its vertical length is denoted by h4.
  • a relationship between the vertical lengths is expressed by h1>h2>h3>h4. Note that the image capturing range may be automatically switched according to information from the lens unit 300 .
  • the vertical length of the image capturing range is changed, and accordingly, the traveling start and end positions of the shutter are also changed. That is, the traveling distance of the shutter is changed, whereby the flash synchronization time is also changed.
  • the time T1 and time T2 are shortened as shown in FIG. 9 . As a result, the flash synchronization time is shortened.
  • the system controller 120 may variably control the threshold values TV0 and TV1 based on the image capturing range. For example, the system controller 120 sets the threshold values TV0 and TV1 to larger values as the vertical length is shorter. In doing this, the threshold values TV0 and TV1 may be changed according to a ratio between the vertical length before the change and the vertical length after the change.
  • execution of the front curtain correction control (second control) is adopted on condition that there is no flicker in the photographing environment.
  • the present variation differs from the first embodiment in the flash synchronization shutter speed-increasing operation process and is the same as the first embodiment in the other respects.
  • FIG. 10 is a flowchart of a variation of the flash synchronization shutter speed-increasing operation process which is performed in the step S 109 in FIG. 6 .
  • a step S 301 the system controller 120 determines whether there is a flicker in the photographing environment by using a known method. Then, if there is no flicker, the system controller 120 proceeds to the step S 201 , whereas if there is a flicker, the system controller 120 proceeds to the step S 206 .
  • the steps S 201 to S 206 are the same as those described with reference to FIG. 7 .
  • the present variation it is possible to obtain the same advantageous effects as provided by the first embodiment in reducing exposure variation between upper and lower end areas of the image when flash light emission photographing is performed while shortening the flash synchronization time. Further, since the front curtain correction control is not performed in a case where there is a flicker, it is possible to suppress degradation of the quality of the photographed image.
  • the predetermined amount of light emission may be changed to a smaller value. That is, in the case where there is a flicker, in addition to the step S 206 , processing corresponding to the step S 204 may be executed.
  • the image capturing apparatus to which the present invention is applied is not limited to the digital camera.
  • the present invention can also be applied to an image capturing apparatus which is not referred to as the digital camera, including a portable device, such as a smartphone and a wearable terminal, an in-vehicle camera, and a security camera.
  • the operation of the camera 1 is controlled by the operations of the components of the camera 1 , such as the image processor 107 , the memory controller 110 , and the system controller 120 , in cooperation with each other, this is not limitative.
  • a program for realizing the above-described process in FIG. 6 may be stored in the main memory 121 in advance. Then, the operation of the camera 1 may be controlled by the system controller 120 or the like, including a microcomputer, that executes the program.
  • the program may be in any of forms including an object code, a program executed by an interpreter, and script data supplied to the OS, insofar as it has a program function.
  • a recording medium for supplying the program may be, for example, a magnetic recording medium, such as a hard disk or a magnetic tape, or an optical/magneto-optical recording medium.
  • Embodiment(s) of the present invention can also be realized by a computer of a system or apparatus that reads out and executes computer executable instructions (e.g., one or more programs) recorded on a storage medium (which may also be referred to more fully as a ‘non-transitory computer-readable storage medium’) to perform the functions of one or more of the above-described embodiment(s) and/or that includes one or more circuits (e.g., application specific integrated circuit (ASIC)) for performing the functions of one or more of the above-described embodiment(s), and by a method performed by the computer of the system or apparatus by, for example, reading out and executing the computer executable instructions from the storage medium to perform the functions of one or more of the above-described embodiment(s) and/or controlling the one or more circuits to perform the functions of one or more of the above-described embodiment(s).
  • computer executable instructions e.g., one or more programs
  • a storage medium which may also be referred to more fully as a
  • the computer may comprise one or more processors (e.g., central processing unit (CPU), micro processing unit (MPU)) and may include a network of separate computers or separate processors to read out and execute the computer executable instructions.
  • the computer executable instructions may be provided to the computer, for example, from a network or the storage medium.
  • the storage medium may include, for example, one or more of a hard disk, a random-access memory (RAM), a read only memory (ROM), a storage of distributed computing systems, an optical disk (such as a compact disc (CD), digital versatile disc (DVD), or Blu-ray Disc (BD)TM), a flash memory device, a memory card, and the like.

Landscapes

  • Physics & Mathematics (AREA)
  • General Physics & Mathematics (AREA)
  • Engineering & Computer Science (AREA)
  • Multimedia (AREA)
  • Signal Processing (AREA)
  • Studio Devices (AREA)
  • Shutters For Cameras (AREA)
  • Exposure Control For Cameras (AREA)
  • Stroboscope Apparatuses (AREA)
US18/452,171 2022-08-23 2023-08-18 Image capturing apparatus capable of reducing exposure variation between upper and lower end areas of image, method of controlling image capturing apparatus, and storage medium Pending US20240077783A1 (en)

Applications Claiming Priority (2)

Application Number Priority Date Filing Date Title
JP2022132614A JP2024030059A (ja) 2022-08-23 2022-08-23 撮像装置およびその制御方法、プログラム
JP2022-132614 2022-08-23

Publications (1)

Publication Number Publication Date
US20240077783A1 true US20240077783A1 (en) 2024-03-07

Family

ID=90060585

Family Applications (1)

Application Number Title Priority Date Filing Date
US18/452,171 Pending US20240077783A1 (en) 2022-08-23 2023-08-18 Image capturing apparatus capable of reducing exposure variation between upper and lower end areas of image, method of controlling image capturing apparatus, and storage medium

Country Status (2)

Country Link
US (1) US20240077783A1 (enrdf_load_stackoverflow)
JP (1) JP2024030059A (enrdf_load_stackoverflow)

Also Published As

Publication number Publication date
JP2024030059A (ja) 2024-03-07

Similar Documents

Publication Publication Date Title
US10791279B2 (en) Control device, control method, and exposure control system
US9996907B2 (en) Image pickup apparatus and image processing method restricting an image stabilization range during a live view operation
US10116876B2 (en) Image capturing method and apparatus, with reduced saturation and improved signal-to-noise ratio based on a dynamic range
US8964106B2 (en) Exposure control device and electronic camera having the same
JP5943561B2 (ja) 撮像装置、その制御方法、および制御プログラム
US7945155B2 (en) Apparatus for capturing images, method of controlling exposure in the apparatus, and computer readable recording medium storing program
JP2017028637A (ja) 撮像装置、その制御方法およびプログラム
JP6758950B2 (ja) 撮像装置、その制御方法とプログラム
JP2010068046A (ja) 撮像装置
JP5371474B2 (ja) 撮像装置、制御方法、及びプログラム
JP5003348B2 (ja) 電子カメラ
US20240077783A1 (en) Image capturing apparatus capable of reducing exposure variation between upper and lower end areas of image, method of controlling image capturing apparatus, and storage medium
US12149833B2 (en) Apparatus, method thereof, and storage medium for adjusting an image quality of an image for live view display
US8467673B2 (en) Imaging apparatus, camera system, and illumination apparatus
US8373766B2 (en) Image shooting device and image shooting method
JP4869801B2 (ja) 撮影装置
JP4597887B2 (ja) 撮影装置
JP5641316B2 (ja) 撮像装置、プログラム、及び撮影方法
US20130194456A1 (en) Imaging device
US11809073B2 (en) Apparatus, control method, and storage medium
US20250274676A1 (en) Image capturing system capable of performing image capturing in desired charge accumulation time in image sensor while suppressing generation of stripes, image capturing apparatus, lighting device, method of controlling image capturing system, and storage medium
JP2011114442A (ja) 電子カメラ
JP7669182B2 (ja) 撮像装置、その制御方法とプログラム
JP2024127017A (ja) 撮像装置および制御方法、プログラム
JP4957580B2 (ja) 撮像装置及びプログラム

Legal Events

Date Code Title Description
STPP Information on status: patent application and granting procedure in general

Free format text: DOCKETED NEW CASE - READY FOR EXAMINATION

AS Assignment

Owner name: CANON KABUSHIKI KAISHA, JAPAN

Free format text: ASSIGNMENT OF ASSIGNORS INTEREST;ASSIGNOR:MATSUMOTO, YUKIHIRO;REEL/FRAME:065142/0244

Effective date: 20230804